It's a ~$50 USB dongle, opensource and available for shipping. Anecdotally, I personally used it for an RF project that need uniform randomness and exhausted /dev/random on the target hardware. It worked fine, if a bit slow for my very specific usecase.
That said, if you want to go even cheaper, seriously consider if you can just stick with /dev/urandom. See http://www.2uo.de/myths-about-urandom/ for an interesting read on why that might just work.
I remember him from the CipherShed project that was trying to reboot TrueCrypt. Discussed securing the build system & distribution. He seemed smart. I have no experience with Tindie, though, so I'd appreciate feedback from anyone that knows about them. He also includes BOM, etc on the GitHub so someone can source and build it themselves.
I'm not normally a paranoid person but EM radiation seems like it's something that it would be easy for someone outside your house in a van to manipulate.
It should be basically impossible for them to manipulate the low bits of the signal. Then you hash it, which makes any bias irrelevant as long as enough bits are random.
You realize modern Intel CPUs include a TRNG, with the RDRAND and RDSEED instructions, for no extra cost. Can't get cheaper than that, if you already have one.
The potential of an NSA backdoor in it is a popular, and entirely possible, conspiracy theory, of course. You'd have to decide for yourself, and compare it to your trust in other options.
It's a ~$50 USB dongle, opensource and available for shipping. Anecdotally, I personally used it for an RF project that need uniform randomness and exhausted /dev/random on the target hardware. It worked fine, if a bit slow for my very specific usecase.
That said, if you want to go even cheaper, seriously consider if you can just stick with /dev/urandom. See http://www.2uo.de/myths-about-urandom/ for an interesting read on why that might just work.